The conception of stress-strength interference model for mechanical reliability analysis is introduced and the reliability model of cylindrical helical spring is given in this paper. Combining the strength degradation model, the phenomenon of spring reliability decreasing with the operation times is investigated, where the reliability of the spring is correlated with the operation times of the high voltage circuit breaker. According to the stress relaxation model and combination of stress relaxation factor which considering the reliability model with strength degradation, the stress-strength interference model considering stress relaxation and strength degradation is built. After that the life of breaker’s energy-storing spring is predicted. Finally, the feasibility of this method is verified by the calculation example of a specific energy-storing spring.